SHAPED PULSES FOR SELECTIVE INVERSION IN SOLID-STATE DEUTERON NMR-SPECTROSCOPY

Double sideband modulation and pulse shaping can be combined to improv e the performance of selective pulses in solid-state deuteron NMR. Eff icient off-resonance selective inversion of deuterons requires simulta neous irradiation of both spin-1 transitions, i.e., at symmetric offse ts from the Larmor frequency (nu(0) +/- Delta). This is best accomplis hed with double-sideband-modulated pulses. Frequency-selective profile s can be improved by shaping the RF pulses. A variety of commonly used selective pulse shapes are evaluated for their applicability to solid -state deuteron powder patterns. A new pulse shape is introduced; the squared isosceles triangle, Generally, pulses with low bandwidth-durat ion product, such as the Gaussian envelope, are found to be the most e ffective for selective inversion in solid-state H-2 NMR, This is a con sequence of the large inhomogeneous quadrupolar interaction and fast, anisotropic spin-spin relaxation. (C) 1996 Academic Press, Inc.